1. Field of the Invention
The present invention relates to a tension regulating device of a sewing machine.
2. Prior Art
conventionally known is a tension regulating device comprising a regulating dial having a dial and a cap having an arrow corresponding to the dial wherein the regulating dial and the cap are provided at the same unit. It was difficult to conform the arrow of the cap to the scale of the regulating dial which sets a reference thread tension and mounts the cap on the regulating dial. Furthermore, this device has the disadvantage that the reference thread tension can not be changed easily.
In the tension regulating device as illustrated in FIGS. 4 and 5, a supporting plate 103 having an arrow 102 is attached by an adhesive or the like to a plate supporter 104 which is mounted on the tip end of the tension regulating shaft 101. In this tension regulating device, the reference thread tension is set separately for each unit. That is, a regulating nut, which is to be screwed into the tension regulating shaft 101 is rotated in one direction or the other to compress or release a tension regulating spring 108 and set the reference thread clamping pressure applied between a pair of tension discs 106 and 107. A regulating dial 110 is inserted into the tension regulating shaft 101 in predetermined relation while a projection 110a thereof is meshed with one of the notches 105a of the outer periphery of the regulating nut 105. The supporting plate supporter 104 is screwed into the tip end of the tension regulating shaft 101 by way of a Belleville spring 111. Thereafter, the scale appearing in the regulating dial 110 is appropriately conformed to the arrow 102 of the supporting plate 103. In such a manner, after the reference thread tension is set per each unit, the base end of the tension regulating shaft 101 is screwed into a frame 109 and attached thereto.
An operation to connect positional deviation between the scale 110b of the regulating dial 110 and the arrow 102, which is carried out before a practical sewing operation, involves an operation to remove the supporting plate 103 from the supporting plate supporter 104 and an operation to attach the supporting plate 103 to the supporting plate supporter 104, which renders the arrow 102 unclear and also renders the supporting plate 103 difficult to be attached to the correct position. The operation to reset the reference thread tension, which was set as set forth above, is troublesome when changing the mesh of the projection 110a with one of the notches 105a of the regulating nut 105 since not only the regulating dial but also the supporting plate 103, the supporting plate supporter 104, which is screwed into the tension regulating shaft 101, and the Belleville spring 111 must be removed.